Valve gear



May 26, 1931. 1- 1. F. PEARSON VALVE GEAR Filed May 21, 192? 2 Sheets-Sheet l INVENTOR HFPearson,

ATTORNEYS May 26, 1931.

H. F. PEARSON VALVE GEAR Filed May 21, 1927 2 Sheets-Sheet 2 v INVENTOR H I'Pearaon,

' ATTORNEYS lllllllllllll! illlllllllllh WITNESS 1. object ofthis invention.

Patented May 26, 1931 PATENT OFFICE HARRY F. PEARSON, OF SANTA RITA, NEW MEXICO VALVE GEAR AppIication filed May 21, 1927. Serial No. 193,228.

This invention relates to valve gears of the type so extensively used on the steam locomotives, although applicable to stationary engines as well, and 'is more particularly concerned with mechanism which improves yalve gear of the Walschaert type by giving 1t the advantage of variable lead.

This result in the specific embodiment of the invention here presented is accomplished by a novel and advantageous mechanism which is operative to shorten the effective length or leverage of the combination lever of a Walschaert valve gear, for example, as the reverse lever is 'moved toward the center of its quadrant. Obviously, variance in the distance between the fulcrum'point of this combination lever and its point of connection with the valve rod, produces variance in the stroke or lead of the valve.

The chief characteristic of the Walschaert valve gear, as is well known, is a constant lead for the valve for all positions of engine cutoff, this resulting in pre-admission of steam to the cylinder as a cushion for the reciprocation of the very heavy moving parts of the engine structure and driving gear. At high speeds this cushioning action is needed but in starting from a stand still it is a draw back for the piston must then operateagainst this same cushioning back pressure of steam ahead or in front of it before the end of its stroke is reached. T o retain the advantages of theVValschaert gear and to improve it in respect to its above cited disadvantages is an Accordingly I have provided mechanism and connections controlled by movements of the tumbling shaft or bell crank lever operated through the reverse lever and effective to give the engine a different amount of lead for each different position of the reverse lever.

In the accompanying drawings forming part of this specification and to be read in connection therewith, I have shown an engine 0 with valve gear of the Walschaert type as' shown) in which it is pivotally mounted, this modified and improved by that ofthe present invention, v s I V Figure 2 is a top plan view of the variable lead gear box which is mounted over the cylinder casting and guide yoke,

Figure 3 is a vertical section taken on the line33 of Fig. 1 with theparts shown on a slightly enlarged scale, 7

Figures 4 and 5 are vertical sections on the lines 4-4, 55, respectively, of Fig. 3. 7

In the drawings the well known and standard parts of the Walschaert valve gear and associated engine parts are shownin dotted lines, Figs. 1 and 3, with the co-operating mechanism of the present invention shown in full lines for the purpose of clear illustration of the application of the invention.

The power cylinder 1 and its superposed valve cylinder 2 have the usual frame associated therewith providing guides for the cross head 3 to which .the end ofthe piston rod 4 is connected. The valve rod 5 extending from the valve cylinder 2 is connected to a yoke 6 (Fig. 3) reciprocating in frame guides 7 and embracing and journaling the upper bifurcated end 8 of the familiar combination lever 9 of the l/Valschaert construction, modified for the purposes of the present invention. To the upper bifurcated end of this combination lever the forward end of the radius rod or ,bar 10 is pivotally connected, the rear end, adjacentto its extremity being provided with the usual link block (not linkblock being mounted to slide in the arcuate slot 11 of the Walschaert type link 12- centrally pivoted in the trunnions formed by portion 14 pivotally'connected to the usual 0 connecting rod 15a oscillated from the 'engine drive wheel (not shown).

The rear end of the radius rod 10 extends beyond the point of its pivotal connection to 05 the block sliding in slot 11 of the link 12 and is pivoted to the lower end of a link bar 15 whose upper end in turn pivotally connects to the rear arm 16 of the bell crank or tumbling shaft lever, pivoted on the engine frame and having its other arm 17 connected at its end by pivoted rod 17 to the reverse lever. This lever acting through its link 15 moves the radius rod in the slot 11 to actuate the valve rod to start the engine and to position the radius rod for subsequent reciprocation through drive wheel operated oscillation of the slotted link 12.

My invention as applied to the construction which I have just outlined proposes to vary the lead of the valve by variably moving the fulcrum and thereby varying the length of the combination lever of the Walschaert gear which controls the lead of the valve, and to do this through mechanism operated through the actuation of the bell crank or tumbling shaft by the reverse lever.

To this end, the lower end of the combination lever 9 is enlarged and slotted on an are at 19, the radius of which is made the length of the arm 20 pivotally mounted at the base of the piston cross-head 3 and having its forward end bifurcated to embrace the slotted end 19 of the combination lever. A pin 21 which extends outwardly through this end of the lever 20 and through slot 19 has its end seated and journalling in the hub 22 at the lower end of what may be termed a fulcrum shifting or leverage varying bar 23 (Fig. This pin constitutes a bearing member and fulcrum for the lower end of the combination lever 9.

The upper end of bar 23 is pivoted to a cross head 24 sliding between vertical guides 25 screwed to the outer face of a gear box 26 which is supported upon the engine frame by a base 27 extending from cylinder casting to guide yoke and appropriately braced. The side of the box 26 between guides 25 is slotted to permit the pin 28 of the bar 23 to extend through into the interior of the case which is best seen in Fig. 3 of the drawings.

This interior is divided by a central partition 29 into two compartments, the partition and rear wall having upper and lower aligned bosses drilled to form bearings. In the lower of these hearings a shaft 30 is journaled, this shaft extending from the inside or rear face through and into the front compartment where it has mounted upon its end a wheel 31 having an offset or eccentric pin 32 projecting therefrom. A connecting rod 33 ournalling at its opposite ends on pins 28 and 33 serves to transmit motion from the wheel 31 to the cross head and bar 23. In the rear compartment of the gear box a gear 34 is pinned on shaft 30 and is in turn engaged and actuated by a segmental rack 35 whose hub 36 is fixed on shaft 37 journalled in the upper aligned bosses of the gear box and extending outwardly from the rear and carrying crank arm 38 to whose bifurcated end is pivoted the front end of a reach rod 39, the rear end of which is pivoted to the bell crank of tumbling shaft lever 16-17 adjacent to its uper end.

The number of teeth in the segmental rack 35 and gear 34 are preferably such as to give the wheel 31 one complete revolution through movement of the bell crank 16-17 from full forward to full backward position, placing cross-head 24 and the fulcrum shifting bar 23 and the forward bifurcated end of arm 20 at their topmost positions, respectively, when the bell crank-arms 1617 are inthe central position shown in Fig. 1. The cross head 24 has its guides 25 extending for a suflicient distance to permit the cross head to move vertically the full distance necessary to give the engine the required lead of the different positions of the reverse lever.

From the foregoing it will be seen that actuation of the reverse lever and bell crank 16-17 for engine starting operation of the valve rod 5, and the subsequent valve rod reciprocation through engine operation will provide a modified and variable valve threw or lead, the bell crank arm 17 moving reach rod 39, rack and pinion 35, 34 and through wheel 31, connecting rod 33 and cross head 24, moving the fulcrum shifting or leverage varying bar 23 vertically and through this vertical movement varying the position of pin 21 and therefore the point in its slot 19 at which the lower end of the combination lever 9 is permitted to turn and fulcrum (see Fig.

Preferably when used in a valve gear combination of the Valschaert type, the connections between the bell crank 1617 operated by the reverse lever and the fulcrum shifting rod 23 will be such as to vary the lead progressively from the maximum at full speed to a minimum at starting and slow speeds.

Vhile it is true that I have shown and described this invention as embodied in a valve gear of the standard Valschaert type as applied to a locomotive, it is applicable also to stationary engines and adaptable to varying types of valve gear within the spirit of the invention and of the appended claims. In other words the structure of the invention may be embodied and applied in a number of different ways and while a specific embodiment and application are shown, it is not my desire or intention so to limit the invention as outlined in the appended claims except as may be necessary in view of the prior art or by the language of a claim.

The lead varying mechanism herein described may be mounted by its base 27 on either side of the engine without change except as to the combination levers which must be made in rights and lefts.

I claim:

1. In a valve gear, the combination with a valve rod, a piston rod, a cross head reciprocated thereby, a depending lever extending at an angle to said valve and piston rods and operatively connected to the valve red at a point adjacent to its upper end, and a radius rod connected to said end of the lever and movable to operate said valve rod, of an arcuately slotted bearing at the lower end of said lever, a link pivotally supported from the cross head for swinging movement of its end in an arc co-incident with that of said arcuate lever slot, a bar mounted for sliding movement in a direction longitudinally of said arcuate slot, a bearing member slidably seating in said arcuate slot and pivotally interconnecting the swinging end of said link and the lower end of said bar, said member providing a movable fulcrum point for said lever, manually operable connections efiective to move said radius rod, determinately intergeared mechanism operatively connected to the other end of said bar and operative to reciprocate the upper end of bar determinately to move said bearing member and fulcrum point, and means for operating said mechanism co-incidently with and through movement of said manually operable connections. 2. In a valve gear, the combination with a valve rod, a piston rod, a cross head thereon, a depending lever extending at an angle to said valve and piston rods and operatively connected to the valve rod at a point adjacent to its upper end, and a valve shifting means connected to saidrend of the lever and movable to operate said valve rod, of an arcuately slotted bearing at the lower end of said lever, a link pivotally supported from the cross head for swinging movement of its end in an arc (Jo-incident with that of the arcuate slot in said lever end, a bar mounted for sliding movement in a direction longitudinally of said arcuate slot, a bearing member slidably seating in said arcuate slot and pivotally interoonnecting the swinging end of said link and lower end of said bar, said bearing member providing a movable fulcrum point for said lever, means co-operating with the upper end of said bar and said valve shifting means determinately to move said bar to shift said fulcrum point co-incidentally with and through actuation of said valve shifting means.

HARRY F. PEARSON. 

